<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<meta name="viewport" content="width=device-width, initial-scale=1">
	<title></title>
	<style type="text/css">
			 *{
			 	margin: 0;
			 	padding: 0;
			 }
			 body{
			 	background: blue;
			 }
			 .box{
			 	width: 400px;
			 	height: 400px;
			 	background: white;
			 	margin: 0 auto;
			 	margin-top: 100px;
			 	position: relative;
			 }
			 .circle{
			 	width: 100px;
			 	height: 100px;
			 	background: white;
			 	border-radius: 50%;
			 	position: absolute;
			 	left: 50%;
			 	margin-left: -50px;
			 	top: -50px;
			 	text-align: center;
			 	line-height: 100px;
			 	font-weight: bolder;
			 	color: #999;
			 }
	</style>
</head>
<body>
	 <!-- 子绝父相：子元素设置绝对定位，父元素设置相对定位 -->
	 <div class="box">
	 	<div class="circle">LOGO</div>
	 </div>
</body>
</html>